\documentclass[12pt]{article}

\usepackage{pstricks} % To use the standard "xcolor" package with PSTricks
\usepackage{pst-node}
\usepackage{pst-plot}

\pagestyle{empty}

\begin{document}
\psset{unit=5mm,linewidth=.1}

\begin{center}
\begin{figure}
\begin{pspicture}(0,0)(10,20) % -.3 due to the coordinates under Ox
\SpecialCoor

\psline[linecolor=red](0,0)(10,10)
\rput(12,10){\psframebox[linecolor=white]{$y = 0$}}
\psline[linecolor=blue](0,-5)(10,5)
\rput(12,5){\psframebox[linecolor=white]{$y = 1$}}
\psline[linecolor=blue](0,5)(10,15)
\rput(12,15){\psframebox[linecolor=white]{$y = -1$}}

\pscircle[fillstyle=solid,fillcolor=green,linecolor=green](5,10){0.2}
\pscircle[linecolor=purple](5,10){0.4}

\pscircle[fillstyle=solid,fillcolor=green,linecolor=green](1,9){0.2}
\pscircle[fillstyle=solid,fillcolor=green,linecolor=green](3,9){0.2}
\pscircle[fillstyle=solid,fillcolor=green,linecolor=green](4,15){0.2}
\pscircle[fillstyle=solid,fillcolor=green,linecolor=green](5,17){0.2}
\pscircle[fillstyle=solid,fillcolor=green,linecolor=green](6,14){0.2}
\pscircle[fillstyle=solid,fillcolor=green,linecolor=green](8,16){0.2}

\pscircle[fillstyle=solid,fillcolor=cyan,linecolor=cyan](9,9.8){0.2}
\pscircle[linecolor=purple](9,9.8){0.4}
\rput(9,11){\psframebox[linecolor=white]{$\xi > 1$}}

\pscircle[fillstyle=solid,fillcolor=cyan,linecolor=cyan](5,4.1){0.2}
\pscircle[linecolor=purple](5,4.1){0.4}
\rput(7,5){\psframebox[linecolor=white]{$\xi < 1$}}

\pscircle[fillstyle=solid,fillcolor=cyan,linecolor=cyan](3,-2){0.2}
\pscircle[linecolor=purple](3,-2){0.4}
\rput(5,-2){\psframebox[linecolor=white]{$\xi = 0$}}

\pscircle[fillstyle=solid,fillcolor=cyan,linecolor=cyan](7,2){0.2}
\pscircle[linecolor=purple](7,2){0.4}

\pscircle[fillstyle=solid,fillcolor=cyan,linecolor=cyan](4,-4){0.2}
\pscircle[fillstyle=solid,fillcolor=cyan,linecolor=cyan](7,0){0.2}
\rput(8.5,0){\psframebox[linecolor=white]{$\xi = 0$}}
\pscircle[fillstyle=solid,fillcolor=cyan,linecolor=cyan](9,1){0.2}


\end{pspicture}
\end{figure}
\end{center}

\end{document}